The invention relates to powder inhalers.
Document EP-0,549,605 B1 discloses a powder inhaler, in particular for medicinal treatment, including an air supply chamber communicating with a conduit leading into a suction mouthpiece. Means is provided for bringing into the conduit, before each use, a dose of powder which is to be inhaled. The air is delivered into the conduit, entrains the powder, passes through the mouthpiece and reaches the user's lungs. The air delivery facilitates the administration of the powder in the lungs without demanding from the user an inspiration effort which said user is sometimes incapable of providing. To ensure that the success of the treatment is optimal, the entire dose of powder must be conveyed deep into the lungs. However, this is only possible if the air is delivered at the exact moment the user inspires. To this end, the inhaler includes a drawer which is slidably movable in the inhalation conduit and sensitive to suction in the mouthpiece. This drawer is connected to a piston of the chamber which it locks in position counter to a compressed return spring. When the patient breathes in, the displacement of the drawer frees the piston, the movement of which generates the flow of air in the conduit for entraining the powder. Thus, the air is delivered in synchronization with the patient's inspiration. However, the mechanism for synchronizing the delivery of the air with the inspiration extends from the conduit as far as the piston and is thus relatively large and complicated.
An object of the invention is to make available a compressed-air powder inhaler which includes a synchronization mechanism of simple structure and of small size which permits instant delivery of air.